1. Field of the Invention
The invention relates generally to vehicle braking systems, and more particularly, to an antiskid system that controls the deceleration of the vehicle wheels and collects information related to the operation of the vehicle braking system.
2. Description of Related Art
Antiskid braking systems have been provided on commercial and large turbine aircraft to aid in the deceleration of aircraft upon landing. Modern antiskid systems typically optimize braking efficiency by adapting to runway conditions and other factors affecting braking to maximize deceleration, corresponding to the level of brake pressure selected by the pilot. In conventional antiskid braking systems, brakes are typically applied mechanically through a metering valve by the pilot. As soon as the wheel brake pressure approaches the skid level, such as when an initial skid is detected, the antiskid control system is initialized.
The electronic control subsystems of an antiskid control system are typically located in the electronic equipment bays of the aircraft along with various other aircraft electronic systems. Though located a distance from the landing gear, operation of a typical antiskid control system relies on measurements of sensors located within the landing gear. Once such sensor is a wheel speed transducer. The wheel speed transducer provides a signal indicative of the velocity of the wheel. Measurements from the wheel speed transducer are fed to the antiskid control system through a complex and lengthy aircraft wiring network where they are processed by an antiskid control unit to produce a wheel velocity signal. The wheel velocity signal is further processed to control an antiskid valve located downstream from the metering valve.
Other sensors may be located within the landing gear to assist in the antiskid control process. For example, an accelerometer may be used to adjust the reference velocity of the antiskid control system to make the reference velocity immune against wheel speed variation caused by gear walk or truck pitch. In addition to antiskid control system related sensors, additional sensors, such as brake temperature sensors, tire pressure sensors and torque sensors, may be located within the landing gear. These sensors provide measurements beneficial in analyzing the condition of landing gear components to determine, for example, the degree of tire wear and brake pad wear. Measurements from these sensors may also prove useful in monitoring pilot performance. For example, insight into a particular pilot's landing performance may be gathered from brake temperature and wheel torque data. All of this data is useful in monitoring the life cycle of braking system and landing gear components and evaluating their cost of operation.
Data provided by these sensors is typically recorded in a data concentrator located in an electronic equipment bay a substantial distance from the wheel. As such, data from these sensors must also pass through the lengthy aircraft wiring network. The need for great lengths of wire from the sensors to both the antiskid control unit and the data concentrator tends to increase the cost and weight of the aircraft. Collection of data from the data concentrator requires access to the data output busses of the electronic equipment bays. This is often inconvenient for the landing gear maintenance crew, in that the data concentrator is located a distance from the landing gear itself.
Hence, those skilled in the art have recognized a need for providing an antiskid control system and data concentrator that is less dependent on complex and lengthy aircraft wiring and is easily accessible to landing gear maintenance personnel. The invention fulfills these needs and others.